Dietary and pharmacological antioxidants in atherosclerosis

The activities of antioxidant nutrients in human plasma depend on the localization of attacking radical species

The oxidation of endogenous antioxidant nutrients in human plasma was determined to examine their activities against free radicals generated in the aqueous and lipid compartments of plasma. Free radicals were induced at a constant rate in the aqueous compartment by the hydrophilic radical generator, 2,2'-azobis-(2-amidinopropane)dihydrochloride (AAPH; 10-20 mmol/L) and in the lipid compartment by the lipophilic radical generator, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (MeO-AMVN; 1-2 mmol/L). The depletion of endogenous plasma antioxidant nutrients (lutein, cryptoxanthin, beta-carotene, lycopene, alpha-tocopherol, ascorbic acid, uric acid) was determined after incubation with either AAPH or MeO-AMVN at 37 degrees C using HPLC. The oxidation of the aqueous and lipid compartments of plasma was selectively monitored by a fluorimetric method using either the hydrophilic probe, 2',7'-dichlorodihydrofluorescein (DCFH) or the lipophilic probe, 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a, 4a-diaza-s-indacene-3-undecanoic acid (BODIPY 581/591). When plasma was incubated with AAPH, the rates of consumption of the antioxidant nutrients were as follows: ascorbic acid > alpha-tocopherol > uric acid > lycopene > lutein > cryptoxanthin > beta-carotene. When plasma was incubated with MeO-AMVN, alpha-tocopherol and carotenoids were depleted at similar rates and ahead of the major water-soluble antioxidants. Our study indicates that the antioxidant nutrients present in both the lipid and aqueous compartments can remove free radicals generated in plasma, and their activity depends on the localization of the attacking radical species.

Monocyte chemoattractant protein-1 involvement in the alpha-tocopherol-induced reduction of atherosclerotic lesions in apolipoprotein E knockout mice

We studied the effects of alpha-tocopheryl acetate supplementation on the development of fatty streaks and its ability to modulate the expression of monocyte chemoattractant protein (MCP)-1 in aortic lesions of apolipoprotein E knockout mice. For this purpose, 16-week-old apolipoprotein E knockout mice received alpha-tocopherol supplementation (800 mg)/kg diet) for 6 weeks. After this time, total and lipoprotein cholesterol in the serum, hepatic tocopherol, aortic lesion area and MCP-1 (protein and mRNA) expression were analysed. Our present results showed that the dietary supplementation with alpha-tocopherol did not reduce serum cholesterol nor change lipoprotein profile, but it reduced the area of the aortic lesion by 55 %. The reduction in the lesion size was correlated with the reduced expression of MCP-1 mRNA and protein, as detected by real-time quantitative polymerase chain reaction and immunohistochemistry respectively. In conclusion, the results obtained here are relevant to the study of atherosclerosis, as they correlate the effectiveness of vitamin E supplementation in inhibiting the plaque formation with diminished expression of MCP-1 at the aortic lesion.

Combined effect of coenzyme Q10 and fenofibrate on forearm microcirculatory function in type 2 diabetes

Arteriopathy is the principal complication of type 2 diabetes mellitus. It develops from endothelial dysfunction, which we have hypothesised occurs in diabetes primarily as a consequence of dyslipidaemia and oxidative stress. Fenofibrate and CoQ may improve endothelial function by regulating dyslipidaemia and oxidative stress, respectively. We therefore aimed to assess the independent and combined effects of fenofibrate and coenzyme Q(10) (CoQ) on endothelium-dependent and endothelium-independent vasodilator function of the forearm microcirculation in type 2 diabetes. Eighty dyslipidaemic type 2 diabetics were randomized to receive fenofibrate (200 mg/daily), CoQ (200 mg/daily), fenofibrate plus CoQ (200+200 mg daily), or placebo for 12 weeks. Forearm microcirculatory function was assessed with venous occlusion plethysmography during the infusion of acetylcholine (ACh), bradykinin (BK), sodium nitroprusside (SNP) and N(G)-monomethyl-L-arginine (L-NMMA) into the brachial artery. Blood flow responses were calculated as area under the curve (AUC). Fenofibrate significantly lowered plasma cholesterol, triglyceride and fibrinogen (P<0.001), and elevated HDL-cholesterol and homocysteine (P<0.001). CoQ did not change plasma isoprostanes, but significantly lowered systolic blood pressure and HbA(1c) (P<0.05). Fenofibrate plus CoQ significantly improved (P<0.05) the AUC for ACh, BK and SNP without significantly altering basal responses to L-NMMA. Fenofibrate or CoQ alone did not significantly alter blood flow responses. Improvements in blood flow were independent of changes in plasma lipids, blood pressure, homocysteine and isoprostanes, but were correlated (P=0.013) with HbA(1c). In conclusion, in this factorial trial we found that only the combination of fenofibrate and CoQ markedly improved endothelial and non-endothelial forearm vasodilator function in dyslipidemic type 2 diabetic patients. The favourable vascular effect of this therapeutic combination could be due to increase in the bioactivity of and/or responses to endothelium-derived relaxing factors, including nitric oxide, and this may entail synergistic stimulation of peroxisome proliferator-activated receptors.

Probucol promotes functional reendothelialization in balloon-injured rabbit aortas

BACKGROUND

Probucol remains the only conventional drug that reduces restenosis after coronary angioplasty. Apart from its weak cholesterol-lowering effect, probucol has antioxidant properties, but it remains unclear how this drug inhibits restenosis.

METHODS AND RESULTS

Aortic balloon-injured New Zealand White rabbits were fed 2% (wt/wt) cholesterol-enriched or normal chow, with 0.75% (wt/wt) probucol (P) or without (controls, C) for 6 weeks. Endothelial denudation of the abdominal aorta was performed at week 3 with a 3F Fogarty embolectomy catheter. The arteries were harvested after week 6 and analyzed for histology, lipids and antioxidants, and endothelial regeneration and function. Probucol significantly decreased aortic intima-to-media ratio (cholesterol-fed: C, 1.10+/-0.08 versus P, 0.70+/-0.10; normal: C, 0.89+/-0.02 versus P, 0.83+/-0.05; P<0.05) and the numbers of proliferating intimal smooth muscle cells and lowered serum cholesterol without altering the proportion of aortic lipids that was oxidized. Probucol promoted endothelial regeneration in the injured aorta in cholesterol-fed rabbits (25% increase in reendothelialization, P<0.05) and in those on normal chow (37% increase, P<0.01). This was associated with both improved endothelial function as assessed by enhanced aortic ring relaxation and cGMP production in response to acetylcholine and decreased intimal thickening.

CONCLUSIONS

Probucol inhibits intimal thickening in balloon-damaged arteries of rabbits by promoting the regeneration of functional endothelium, without affecting the proportion of aortic lipids that was oxidized. This novel in vivo finding helps explain how probucol inhibits restenosis after coronary angioplasty and highlights potential new targets for therapeutic intervention.

Juice and phenolic fractions of the berry Aristotelia chilensis inhibit LDL oxidation in vitro and protect human endothelial cells against oxidative stress

Oxidative modification of low-density lipoprotein (LDL) particles is a key event in the development of atherosclerosis. Oxidized LDL induces oxidative stress and modifies gene expression in endothelial cells. Berries constitute a rich dietary source of phenolic antioxidants. We found that the endemic Chilean berry Aristotelia chilensis (ach) has higher phenol content and scores better for total radical-trapping potential and total antioxidant reactivity in in vitro antioxidant capacity tests, when compared to different commercial berries. The juice of ach is also effective in inhibiting copper-induced LDL oxidation. In human endothelial cell cultures, the addition of ach juice significantly protects from hydrogen peroxide-induced intracellular oxidative stress and is dose-dependent. The aqueous, anthocyanin-rich fraction of ach juice accounts for most of ach's antioxidant properties. These results show that ach is a rich source of phenolics with high antioxidant capacity and suggest that it may have antiatherogenic properties.

The use of antioxidant supplements in coronary heart disease

There is clear evidence of lipoprotein oxidation in atherosclerotic lesions. Animal studies and observational prospective human cohort studies have been interpreted as supporting a role for antioxidants in the prevention of coronary heart disease (CHD). However, firm recommendations to take antioxidant supplements to treat or prevent CHD require evidence derived from randomised controlled studies. In primary prevention studies, low dose alpha-tocopherol does not reduce the incidence of coronary events (ATBC study), and beta-carotene either has no effect or increases the incidence of coronary events and cancer death (ATBC, CARET, Physician's Health studies). Secondary preventions, those with smaller populations and shorter duration of follow up have shown some benefit from alpha-tocopherol (CHAOS, SPACE), but larger randomised studies indicate no benefit from treatment with alpha-tocopherol (HOPE, GISSI, PPP). Recent studies with antioxidant combinations also show no benefit (HATS, MPS). On the basis of these data, supplements of alpha-tocopherol and beta-carotene cannot be recommended for the treatment or prevention of CHD. Fundamental and applied research may yet find a role for antioxidant supplements in the treatment of coronary disease. However, this will require positive results from combined antioxidant studies currently in progress, and the targeting of oxidative processes that operate in the artery wall and cause or contribute to disease.

Risks and benefits of soy phytoestrogens in cardiovascular diseases, cancer, climacteric symptoms and osteoporosis

Phytoestrogens, plant chemicals classified as isoflavones, coumestans and lignans, display estrogen-like activity because of their structural similarity to human estrogens and exhibit high affinity binding for the estrogen receptor beta. They are common components of food items such as grains, beans, fruits and nuts. Isoflavones are primarily found in soybeans and foods made from soy. In particular, significant therapeutic properties have been generally attributed to soy isoflavones, but most of the claims have been poorly, or not at all, confirmed by well designed clinical trials. Such is the case of the purported role of soy isoflavones in reducing plasma cholesterol levels. This link is now not supported by many authors or by appropriately designed clinical studies. The role of isoflavones in cancer prevention, particularly of tumours under endocrine control (breast, prostate and others) is again only supported by weak to nonexisting clinical evidence. A similarcase is that of the prevention/treatment of postmenopausal symptoms and osteoporosis. Disturbing data have been reported on potential negative effects of soy isoflavones on cognitive function in the aged, particularly relating to tofu intake. Recent studies have finally indicated a potential role for soy isoflavones in inducing chromosomal changes in cells exposed in vitro and potentiating chemical carcinogens. These findings may not, however, be extrapolated to clinical conditions. Available data do not appear to unequivocally support beneficial effects of soy isoflavones, and warn against their wide use, in the absence of satisfactory clinical findings.

Low-density lipoprotein-antioxidant constituents of Saururus chinensis

A new diarylbutane lignan, saururin A (1), and a known 8-O-4'-type neolignan, machilin D (2), were isolated from a total methanol extract of the underground parts of Saururus chinensis. The structures of 1 and 2 were elucidated by spectroscopic data analysis. Compounds 1, 2, and virolin (3) (the methyl ether of 2) exhibited significant low-density lipoprotein (LDL)-antioxidant activity in the thiobarbituric acid-reactive substance (TBARS) assay with IC(50) values of 8.5, 2.9, and 4.3 microM, respectively.

Protection by quercetin and quercetin 3-O-beta-D-glucuronide of peroxynitrite-induced antioxidant consumption in human plasma low-density lipoprotein

Effect of quercetin and its conjugated metabolite quercetin 3-O-beta-D-glucuronide (Q3GA), on peroxynitrite-induced consumption of lipophilic antioxidants in human plasma low-density lipoprotein (LDL) was measured to estimate the role of dietary flavonoids in the defense system against oxidative modification of LDL based on the reaction of nitric oxide and superoxide anion. Synthesized peroxynitrite-induced consumption of endogenous lycopene beta-carotene and alpha-tocopherol was effectively suppressed by adding quercetin aglycone into LDL solution. Q3GA also inhibited the consumption of these antioxidants effectively. These results indicate that dietary quercetin is capable of inhibiting peroxynitrite-induced oxidative modification of LDL in association with lipophilic antioxidants present within this lipoprotein particle.

Correlation between intima-to-media ratio, apolipoprotein B-100, myeloperoxidase, and hypochlorite-oxidized proteins in human atherosclerosis

The oxidative modification of low-density lipoprotein (LDL) is thought to contribute to atherogenesis, and there is evidence that oxidants derived from myeloperoxidase (MPO) contribute to such oxidative damage. Using human iliac arteries we investigated the relationship between lesion stage indicated by the intima-to-media (I/M) ratio and the presence of apolipoprotein B-100 (apoB, a marker for LDL), MPO, and hypochlorite (HOCl)-oxidized proteins identified by immunohistochemistry in the intima, media, and adventitia. More staining for apoB, MPO, and HOCl-oxidized proteins was observed in diseased than healthy vessels. Diseased segments also stained more for the three parameters than healthy segments in the same diseased vessel, highlighting the variability that can occur within a single cross-section of a vessel. However, significant positive correlation between I/M ratio and positive staining for apoB, MPO, and HOCl-oxidized proteins in different segments of individual arteries were apparent in segments with an I/M ratio of > 1.8. Also, the overall extent of intimal staining for apoB, MPO, and HOCl-oxidized proteins increased with increasing I/M ratio. In addition, the extent of apoB staining was greater and appeared at comparatively lower I/M ratios than that of MPO and HOCl-oxidized proteins. Our results support a contribution to atherogenesis of all three parameters assessed, although MPO and HOCl-oxidized proteins appear to participate in the disease process at a later stage than apoB.

Oxidants and antioxidants in atherosclerosis

The oxidative theory suggests that LDL oxidation contributes to atherogenesis, implying that attenuation of this process by antioxidants should decrease atherosclerosis. However, a causative link between LDL oxidation and atherogenesis is not firmly established. It requires the identification of the oxidants that are responsible for the initiation of LDL oxidation, and an understanding of the modified moieties that are responsible for the proatherogenic activities of oxidized LDL. The present review summarizes recent data on potential biological oxidants for LDL in the vessel wall, and discusses the antiatherogenic role(s) of selected antioxidants.

Pomegranate juice supplementation to atherosclerotic mice reduces macrophage lipid peroxidation, cellular cholesterol accumulation and development of atherosclerosis

Inhibition of lipid peroxidation contributes to the attenuation of macrophage cholesterol accumulation, foam-cell formation and atherosclerosis. Evidence suggests that nutritional antioxidants such as pomegranate juice (PJ) can contribute to the reduction of oxidative stress and atherogenesis. The goals of the present study were to determine whether such beneficial effects of PJ exist when supplemented to apolipoprotein E-deficient (E(0)) mice with advanced atherosclerosis and to analyze the antiatherosclerotic activity of a tannin-fraction isolated from PJ. Mice (4-mo-old) were supplemented with PJ in their drinking water for 2 mo and compared with age-matched placebo-treated mice, as well as to young (4-mo-old) control mice, for their mouse peritoneal macrophage (MPM) oxidative state, cholesterol flux and mice atherosclerotic lesion size. PJ supplementation reduced each of the proatherogenic variables determined in the present study compared with age-matched placebo-treated mice. It significantly induced serum paraoxonase activity and reduced MPM lipid peroxide content compared with placebo-treated mice and control mice. PJ administration to E(0) mice significantly reduced the oxidized (Ox)-LDL MPM uptake by 31% and MPM cholesterol esterification and increased macrophage cholesterol efflux by 39% compared with age-matched, placebo-treated mice. PJ consumption reduced macrophage Ox-LDL uptake and cholesterol esterification to levels lower than those in 4-mo-old, unsupplemented controls. PJ supplementation to E(0) mice with advanced atherosclerosis reduced the lesion size by 17% compared with placebo-treated mice. In a separate study, supplementation of young (2-mo-old) E(0) mice for 2 mo with a tannin fraction isolated from PJ reduced their atherosclerotic lesion size, paralleled by reduced plasma lipid peroxidation and decreased Ox-LDL MPM uptake. PJ supplementation to mice with advanced atherosclerosis reduced their macrophage oxidative stress, their macrophage cholesterol flux and even attenuated the development of atherosclerosis. Moreover, a tannin-fraction isolated from PJ had a significant antiatherosclerotic activity.

Dietary cosupplementation with vitamin E and coenzyme Q(10) inhibits atherosclerosis in apolipoprotein E gene knockout mice

Intimal oxidation of LDL is considered an important early event in atherogenesis, and certain antioxidants are antiatherogenic. Dietary coenrichment with vitamin E (VitE) plus ubiquinone-10 (CoQ(10), which is reduced during intestinal uptake to the antioxidant ubiquinol-10, CoQ(10)H(2)) protects, whereas enrichment with VitE alone can increase oxidizability of LDL lipid against ex vivo oxidation. In the present study, we tested whether VitE plus CoQ(10) cosupplementation is more antiatherogenic than either antioxidant alone, by use of apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet without (control) or with 0.2% (wt/wt) VitE, 0.5% CoQ(10), or 0.2% VitE plus 0.5% CoQ(10) (VitE+CoQ(10)) for 24 weeks. None of the supplements affected plasma cholesterol concentrations, whereas in the VitE and CoQ(10) groups, plasma level of the respective supplement increased. Compared with control, plasma from CoQ(10) or VitE+CoQ(10) but not VitE-supplemented animals was more resistant to ex vivo lipid peroxidation induced by peroxyl radicals. VitE supplementation increased VitE levels in aorta, heart, brain, and skeletal muscle, whereas CoQ(10) supplementation increased CoQ(10) only in plasma and aorta and lowered tissue VITE: All treatments significantly lowered aortic cholesterol compared with control, but only VitE+CoQ(10) supplementation significantly decreased tissue lipid hydroperoxides when expressed per parent lipid. In contrast, none of the treatments affected aortic ratios of 7-ketocholesterol to cholesterol. Compared with controls, VitE+CoQ(10) supplementation decreased atherosclerosis at the aortic root and arch and descending thoracic aorta to an extent that increased with increasing distance from the aortic root. CoQ(10) significantly inhibited atherosclerosis at aortic root and arch, whereas VitE decreased disease at aortic root only. Thus, in apoE-/- mice, VitE+CoQ(10) supplements are more antiatherogenic than CoQ(10) or VitE supplements alone and disease inhibition is associated with a decrease in aortic lipid hydroperoxides but not 7-ketocholesterol.

Vitamin E inhibition of platelet aggregation is independent of antioxidant activity

Vitamin E is the principal lipid-soluble antioxidant in human plasma, and some studies indicate that it may provide cardiovascular protection. To investigate putative mechanisms for vitamin E in this regard, the effect of vitamin E on vascular function and platelet aggregation was examined. In animal models of endothelial dysfunction, vitamin E improved the activity of endothelium-derived nitric oxide, and this effect was not dependent upon the antioxidant protection of LDL. In fact, vitamin E improved endothelial function in part due to the inhibition of protein kinase C (PKC) stimulation. This activity of vitamin E was examined in platelets, and vitamin E inhibited platelet aggregation in part through a mechanism that involves PKC. Moreover, the platelet inhibitory activity of vitamin E was independent of its antioxidant action because platelet inhibition was still observed with isoforms of vitamin E that were devoid of antioxidant activity.

Genistein prevents the glucose autoxidation mediated atherogenic modification of low density lipoprotein

Hyperglycemia has been assumed to be responsible for oxidative stress in diabetes. In this respect, glucose autoxidation and advanced glycation end products (AGE) may play a causal role in the etiology of diabetic complications as e.g. atherosclerosis. There is now growing evidence that the oxidative modification of LDL plays a potential role in atherogenesis. Glucose derived oxidants have been shown to peroxidise LDL. In the present study, genistein, a compound derived from soy with a flavonoid chemical structure (4', 5, 7-trihydroxyisoflavone) has been evaluated for its ability to act as an antioxidant against the atherogenic modification of LDL by glucose autoxidation radical products. Daidzein, (4',7-dihydroxyisoflavone) an other phytoestrogen of soy, was tested in parallel. Genistein--in contrast to daidzein--effectively prevented the glucose mediated LDL oxidation as measured by thiobarbituric acid-reactive substance formation (TBARS), alteration in electrophoretic mobility, lipid hydroperoxides and fluorescence quenching of tryptophan residues of the lipoprotein. In addition the potential of glucose-oxidized LDL to increase tissue factor (TF) synthesis human endothelial cells (HUVEC) was completely inhibited when genistein was present during LDL oxidative modification by glucose. Both phytoestrogens did not influence the nonenzymatic protein glycation reaction as measured by the in vitro formation of glycated LDL. As the protective effect of genistein on LDL atherogenic modification was found at glucose/genistein molar ratios which may occur in vivo, our findings support the suggested beneficial action of a soy diet in preventing chronic vascular diseases and early atherogenic events.

In vitro evaluation of antioxidant activity by electrophoresis and high performance liquid chromatography

Two methods for the analysis of antioxidants, based on polyacrylamide gel electrophoresis (PAGE) and gel permeation high performance liquid chromatography (HPLC) were developed. Both of them exploit the variations of the signal (band or peak) given by human serum albumin (0.2% w/v in 100 mM sodium phosphate pH 7) upon oxidation with hypochlorite (1% of a solution containing 4% active Cl), quantitatively determined by densitometric analysis or peak integration. Based on such changes, two formulas were defined which allowed the determination of the antioxidant activity of ascorbic acid (EC(50,PAGE)=4.8x10(-4) M, EC(50,HPLC)=3.6x10(-4) M), glutathione (EC(50,PAGE)=1.5x10(-4) M, EC(50,HPLC)=2.0x10(-4) M) and melatonin (EC(50,PAGE)=5.2x10(-4) M, EC(50,HPLC)=3.2x10(-4) M), chosen as reference compounds. A good correlation was found between the activities of these substances in the two assays, which are also in good agreement with literature data, indicating that the two methods are essentially equivalent. These assays could be useful for the screening of new antioxidant drugs for pathological conditions such as cataract, rheumatic diseases, atherosclerosis and Alzheimer's disease.

Therapeutic potential of plant sterols and stanols

Products enriched with plant sterol and stanol esters selectively lower LDL cholesterol. Consumption appears to be safe, and these functional foods thus have great potential for cardiovascular risk management. Although values remain within the normal range, one possible concern is that they lower lipid-standardized concentrations of the plasma carotenoids. Whether this affects health in the longer-term or in selected patient groups is not known. Therefore, especially in view of the increasing number of functional foods that will be on the market in the very near future, there is a clear need to establish an effective post-marketing safety net.

Metabolism of oxidized LDL by macrophages

Oxidation products of lipids and proteins are found in atherosclerotic plaque and in macrophage foam cells. Macrophages avidly endocytose in-vitro oxidized LDL and accumulate sterols. What is the evidence that such a process is involved in in-vivo foam cell formation? The present review surveys current knowledge on the metabolism of oxidized LDL by macrophages, and the types, amounts and location of oxidation products that accumulate in these cells. Comparable studies of lesion lipoproteins and foam cells indicate that limited extracellular lipoprotein oxidation, perhaps followed by more extensive intracellular oxidation subsequent to uptake by macrophages, is a more likely scenario in vivo.

Low density lipoprotein oxidation, antioxidants, and atherosclerosis

Oxidized low density lipoproteins (LDLs) are believed to be the most atherogenic form of LDL. However, although a number of experimental data support this concept, the protective role of antioxidants that may prevent LDL oxidation in atherosclerosis is only partially confirmed by studies in humans. Observational and epidemiologic data as well as randomized trials failed to provide clear-cut indications because of mixed results on the protective role of antioxidants against cardiovascular diseases. In spite of the lack of a general consensus, recent data reinforce the concept that a regular intake of antioxidants present in food blocks the progression of atherosclerosis and that the reduced oxidisability of LDL may represent a good marker to follow the action of antioxidants. When it becomes possible to monitor the efficacy of any antioxidant therapy with validated markers of oxidation, the potential influence of vitamins and antioxidants on coronary artery disease will eventually be resolved.

The oxidative modification hypothesis of atherogenesis: an overview

The literature relating lipid and lipoprotein oxidation to atherosclerosis has expanded enormously in recent years. Papers on the "oxidative modification hypothesis" of atherogenesis have ranged from the most basic studies of the chemistry and enzymology of LDL oxidation, through studies of the biological effects of oxidized LDL on cultured cells, and on to in vivo studies of the effects of antioxidants on atherosclerosis in animals and humans. The data in support of this theory are mounting but many key questions remain unanswered. For example, while it is generally agreed that LDL undergoes oxidation and that oxidized LDL is present in arterial lesions, it is still not known how and where LDL gets oxidized in vivo nor which of its many biological effects demonstrable in vitro are relevant to atherogenesis in vivo. This brief review is not intended to be comprehensive but rather to offer a perspective and a context for this Forum. We discuss the strengths and weaknesses of each line of evidence, try to identify areas in which further research is needed, assess the relevance of the hypothesis to the human disease, and point to some of the potential targets for therapy.